A. Field of Invention
This invention pertains to the art of methods and devices used to spread granular material on ground surfaces, and more specifically to a granular spreader assembly using an auger that prevents granular material flow when the auger is not rotating.
B. Description of the Related Art
Granular spreader assemblies that spread granular material on ground surfaces are well known. One example is provided in U.S. Pat. No. 6,715,703 titled Spreader (“the '703 patent”) which is incorporated herein by reference. The '703 patent discloses a granular spreader assembly that has a storage container (hopper) that holds granular material, such as salt. The storage container is supported to a vehicle. A portion of FIG. 7 from the '703 patent is shown in FIG. 12 which shows the storage container 1 having an opening 2 through which the granular material flows when exiting the storage container 1. A tube 3 has an inner surface defining an opening 4 that communicates with the opening 2 in the storage container 1. An auger 5 is positioned within the tube 3 and has a spiral blade 6. Motor 7 is used to rotate the auger 5 and a spreader plate 8. When rotated, the auger 5 moves or flows the granular material from the storage container 1, along the spiral blade 6, through the opening 4 in the tube 3, and onto the spreader plate 8. If the spreader plate 8 is rotated, the granular material contacts the spreader plate 8 and is then spread onto the ground surface.
The granular spreader assembly shown in FIG. 12, and others like it, generally work well for their intended purposes. They have a problem, however, that commonly occurs when the vehicle transporting the granular spreader assembly comes to a stop, such as at a stop sign or traffic light. When the vehicle stops, the continued spreading of the granular material at that location must also stop or that location will be over covered with granular material. Such over covering is a waste of granular material and may be detrimental to the ground surface at that location.
To address this problem it is known to stop the rotation of the auger and the spreader plate when the vehicle comes to a stop. While this action stops the wide disbursement of the granular material, it does not stop the flow of the granular material onto the ground surface. With reference again to FIG. 12, the granular material continues to flow because there is a gap between the radial outer edge of the spiral blade 6 and the tube surface defining the tube opening 4 that permits the granular material to flow therethrough. This gap is visible in FIG. 12. The granular material also continues to flow because the surface of the spiral blade 6 is smooth (typically made of a smooth metal) permitting the granular material to flow on the smooth surface of the spiral blade 6 through the opening 4 in the tube 3.
One potential solution is to reduce the gap (or clearance) between the radial outer edge of the spiral blade and the tube surface defining the tube opening. While this “solution” may have merit in a workshop setting where working conditions are ideal (a warm environment, clean working conditions, etc.) it has little or no merit in actual use where the working conditions are not ideal (very cold in winter, dirty, etc.). In actual “real world” use such a small clearance could not be maintained and soon the spiral blade would contact the tube which would wear if not damage the auger and/or the tube. Such contact would also require additional power to rotate the auger against the resultant excessive friction.
What is needed, then, is a granular spreader assembly that stops the flow of granular material when the rotation of the auger is stopped and that is useful in “real world” working conditions.